Surface treatment of high speed steel metal cutting tools and the product thereof

ABSTRACT

The subject invention provides a method of treating the working surfaces of high speed steel metal cutting tools to reduce the friction between the surface of the cutting tool and the workpiece and/or the chip and the novel tool produced thereby. The method involves a transformation of the working surface on the steel tool which transformation involves the removal of the multitude of tiny carbide particles that appear in random positions on the working surface. This modified surface layer from which the carbide particles are removed leaves a honeycomb like hole structure where they were, extends to a depth equal to about the average size of carbide particles, at most in the low hundred thousandths of an inch. The removal of this surface layer of carbide particles appears to reduce friction between the active tool surfaces and the workpiece and/or chip is substantially reduced, with consequent reduction in buildup of material on the edge of the tool and reduction of friction of the tool with the chip and/or the workpiece. The process of the invention is advantageous in the surface treatment of high speed steel cutting tools such as twist drills and the like. It is particularly advantageous for the treatment of drills employed to drill holes into soft, gummy metals like aluminum, copper, titanium, and some stainless steels and the like, but is not limited thereto. The high speed steels employed for making the metal-cutting tools herein disclosed comprise a major proportion of iron, containing carbon, and alloying metals known as &#39;&#39;&#39;&#39;carbide formers&#39;&#39;&#39;&#39; including molybdenum, tungsten, chromium and vanadium. Cobalt may also be present. These alloying elements are suitably proportioned to provide the particular properties desired for a specific tool as is well understood in the art.

limited States Patent 11 1 Novosel et al.

1451 Oct. 23, 1973 Donald 0. Erskine, Lyndon Center, both of Vt.

[73] Assignee: Vermont American Corporation, Louisville,'l(y.

[22] Filed: Sept. 2, 1971 [21] Appl. No.: 177,338

52 US. 01. 204/141.5, 204/145 R 51 Int. Cl. c2311 3/02, c230 1/04 [58]Field of Search 204/140, 145 R, 141.5,

[56] References Cited UNITED STATES PATENTS 2,078,869 4/1937 Oplinger204/145 R 2,915,444 12/1959 .Meyer 3,207,683 9/1965 Hermann .I. 204140.5

FOREIGN PATENTS OR APPLICATIONS 200,740 1 1939 Switzerland 7 PrimaryExaminerT. Tufariello Attorney-lohn A. Dienner et a1.

57 ABSTRACT The subject invention provides a method of treating theworking surfaces of high speed steel metal cutting tools to reduce thefriction between the surface of the cutting tool and the workpieceand/or the chip and the novel tool produced thereby. The method involvesa transformation of the working surface on the steel tool whichtransformation involves the removal of the multitude of tiny carbideparticles that appear in random positions on the working surface. Thismodified surface layer from which the carbide particles are removedleaves a honeycomb like hole structure where they were, extends to adepth equal to about the average size of carbide particles, at most inthe low hundred thousandths of an inch. The removal of this surfacelayer of carbide particles appears to reduce friction between the activetool surfaces and the workpiece and/or chip is substantially reduced,with consequent reduction in buildup of material on the edge of the tooland reduction of friction of the tool with the chip and/or theworkpiece.

The process of the invention is advantageous in the surface treatment ofhigh speed steel cutting tools such as twist drills and the like. Itis-particularly advantageous for the treatment of drills employed todrill holes into soft, gummy metals like aluminum, copper, titanium, andsome stainless steels and the like, but is not limited thereto.

I The high speed steels employed for making the metal-cutting toolsherein disclosed comprise a major proportion of iron, containing carbon,and alloying metals known as carbide formers including molybdenum,tungsten, chromium and vanadium. Cobalt may also be present. Thesealloying elements are suitably proportioned to provide the particularproperties desired for a specific tool as is well understood in the art.

5 Claims, 7 Drawing Figures 1 13 RECTIFIER (-1 'E' S (-5 0-9 VOLTS 0-500AMPS. m. 6:232 e /2 v A TIMER NaCN J NQOH START MINUTES H2O STOP SWITCHANODE CATHODE SURFACE TREATMENT OF HIGH SPEED STEEL METAL CUTTING TOOLSAND THE PRODUCT THEREOF BACKGROUND OF THE INVENTION The art is aware ofthe difficulties brought about by the buildup of material from theworkpiece upon the edge of a metal cutting tool.- The friction resultingfrom the high unit pressure between the cutting edge and the workpiece,and the abrading effect of the chips on the working face of the toolproduce high temperatures on/or adjacent the cutting edge whichaccelerates wear and causes failure in the performance of the tool.

This difficulty is encountered in high degree in respect of tools suchas twist drills employed to drill deep holes in soft, gummy metals. Thechip which is coherent and wire-like must be pushed out through therestricted passageways permitted by the flutes of the drill, or exitpassageways of the particular tool involved.

The art has previously developed certain surface treatments ,forreducing friction and prolonging the working life of a tool employed forthis type of work. The surface treatment of the present invention hasshown, in comparative tests, a marked superiority over known methods ofsurface treatment of high speed steel metal cutting tools, particularlysuch as twist drills.

In the'manufacture of twist drills, grindingor mill-ing the flutes tothe final dimensions is the general practice. The surface left bygrinding or milling, as seen under suitable magnification, is rough dueto ridges and grooves left by the abrasive or cutter, and this augmentsfriction to the flow of the chip into and through the flutes to theoutside of the hole.

One proposal of the prior art is to electropolish the surface of thedrill. It leaves the surface clean and bright. It appears to reduce theridges and grooves produced by the grinding or milling operation andprovides an attractive,.clean metal surface. By itself it has nosubstantial effect upon the coefficient of friction with the chip orworkpiece.

Chromium plating of the surface of the drill has been introduced. Thisputs a covering layer of hard, smooth chromium on the surface. However,being a layer, it tends to separate under heavy stresses.

Steam oxidation of the surface of the drill is known. This produces alayer of oxide which is of a character different from that of the bodyof the metal and it also tends to flake and separate under stress.

High speed steels employed for metal cutting tools of the type hereinreferred to follow two general types, (1) the predominantly molybdenumhigh speed steels and (2) the predominantly tungsten high speed steels.However, additional alloy metals such as chromium, vanadium and cobaltare also used to impart desired properties. These alloying metals as aclass are sometimes termed carbide formers since the presence of any ofthem promotes the formation of carbides. We have discovered that inrespect of high speed steel metal cutting tools employing alloycompositions which result in the formation of carbides, that these tinycarbide particles exposed on and substantially flush with the workingsurfaces of such steel tools appear to be responsible in large part forthe friction resulting from the pressure and flow of the chip upon the.cutting tool. In the operation of cutting tools such as twist drills,the relatively high angle which'the chip makes with the advancing edgeof the point and the high pressure and speed of operation in buildup ofmaterial of the workpiece on the front edge of the cutting tool withincreased friction between the chip and the cutting tool results in hightemperature and increasing rate of buildup on the cutting edge. Theaction is cumulative.

SUMMARY OF THE INVENTION We have discovered that friction inherent inthe operation of a high speed steel metal-cutting tool, which includescarbide formers in its composition, upon a metal workpiece can bereduced by a surface treatment of the cutting tool which removes thetiny carbide particles from the surface layer of the working surface ofthe tool such as a twist drill following the grinding operation whichbrings the cutting tool to itsworking form.

Although the invention is applicable to other specific cutting toolsmade of high speed steel for use in a wide variety of metal cuttingoperations, the application of the process of the present invention to aspecific tool is described in connection with the preparation andoperation of high speed steel twist drills.

It is in connection with the use of twist drills required to drill deepholes of small as well as large diameter in soft,gummy metals thatapplication of the present surface treatment to a high speed steel toolshows exceptional superiority to other methods of production of a toolfor the same purpose. The process of the invention involves subjectingthe tool, such as a steel twist drill, after grinding to finished sizeand cleaning the surface, to electrolysis in an electrolytic cell withan aqueous solution of sodium hydroxide and sodium cyanide insubstantially equal proportions wherein the tool serves as an anode inthe bath. The electrolytic treatment levels off the ridges and groovesleft by the finish grinding and removes from the face of the metal themultitude of tiny carbide particles that are present in great numbersper unit area. In this microscopically thin modified surface layer, tinyholes remain exactly where these carbide particles were formerlylocated. Under the influence of the electrolytic action it appears thatthe sodium hydroxide attacks and dissolves the exposed surface carbides,while the sodium cyanide etches the metal matrix in which these carbidesare embedded. Time in this electrolytic bath is a factor. The longer thetime the greater the depth of the action on the tool. More metal matrixwould be etched away exposing more tiny carbide particles that would bedissolved. Ultimately the tool would be destroyed for useful purposes.Under ideal conditions timing would be adjusted so that actually onlythose tiny carbide particles exposed on the surface of the finish groundtoo] were dissolved, thus forming the desired modified surface layer.The treatment generally reveals lines that appear to be grain-likeboundaries in the metal matrix. There is question as to whether theselines actually are grain boundaries as known in the art of metallurgy.All of these conditions related are as observed under scanning electronbeam microscopy. I

Comparative tests of drills prepared according to the surface treatmentsof the prior art with drills treated in accordance with the presentinvention have shown that the drills treated in accordance with thepresent invention have a much longer working life than drills treatedaccording to processes of the prior art. This extended life more thanpays for the cost of the treatment as per the present invention.

The process of the present invention produces a novel surface on thecutting tool and produces a lubricative, anti-weld and anti-frictionproperty of the treated surface of the tool. This reduces the buildupand galling of the cutting edge and chip-engaging face of the toolresulting in lower cutting temperatures and longer cutting life. Theprocess of the invention does not deposit any additive material on thecutting tool surface but permanently transforms the surface of the toolavoiding the possibility of peeling or flaking or deterioration due tocoolants, oils and chemicals.

Superiority of drills of the present invention over the prior art showsup also in drilling harder materials such as stainless steels and eventhe abrasive and hard cast iron.

The requirements of the drill as a metal cutting tool find parallelrequirements in other metal cutting tools such as thread-cutting taps,reamers, end milling cutters, combined drill and countersink and thelike. This is true particularly in those cases where the buildup ofmaterial on the cutting edge interfaces with clean, sharp cutting andfree-flowing chip removal under heavy-duty cutting of the workpiece bythe tool.

OBJECTS OF THE INVENTION The chief object of the present invention is toprovide a surface treatment for high speed steel metal cutting toolswhich will extend the useful life' of the tool so treated and theimproved tool produced by said treatment.

A further object of the invention is to reduce the buildup ofmaterialupon the cutting edge of the tool so treated;

A further object is to reduce the abrading effect of the chip upon theface and chip passageways of the tool.

A further object is to prevent the buildup of high temperatures upon theface and cutting edge of the tool by treatment in accordance with thepresent invention.

A further object is to provide an electrolytic treatment of high speedsteel cutting tools which will remove carbide particles from the workingsurface of the tool.

A further object is to provide an electrolytic surface treatment fortwist drills and the like to prolong the useful life of the same.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a highspeed steel twist drill of known form but which has received the surfacetreatment of the present invention; it is slightly gray in appearance;

FIG. 2 is an end view of the drill of FIG. 1 on an enlarged scale takenfrom the right of FIG. 1; FIGS. 1 and 2 show the appearance of the drillafter drilling a predetermined number of holes through an aluminum testblock;

FIG. 3 is a side elevation of a drill of the same size and form as thatof FIG. 1 but without having received the surface treatment of thepresent invention; this shows the condition of the untreated drill aftercompleting only a part of the predetermined number of holes through theaforesaid aluminum test block having the chips welded at their innerends to the cutting edges on the point of the drill, said chips lyingpartly within the flutes of the drill and extending outside the flutesbeyond the hole drilled;

FIG. 4 is an end elevation on an enlarged scale of the drill and chipsof FIG. 3 taken from the right of FIG.

FIG. 5 is a circuit diagram of an electrolytic cell and power supply forapplying the surface treatment of the invention to produce drills of theinvention;

FIG. 6 is a plan view at 3,000X of a small area of the flute surface ofa twist drill of the same form and composition as the drill of FIG. 1prior to the application of the electrolytic treatment of the invention.The purpose is to show the typical distribution of the tiny carbideparticles on the working surface of the twist drill. In order to do thisthe matrix was slightly etched away to expose these carbide particles.The sketch was made from a scanning electron beam microscopicphotograph.

FIG. 7 is a plan view at 3,000X of the same area as that shown in FIG. 6after the same surface, shown in FIG. 6, has been treated by the processof the invention. This sketch was also made from a photograph under thesame circumstances as explained for FIG. 6. Note that we now have tinyholes instead of carbide particles, that the layout pattern is the sameas in FIG. 6 and the size and shape of the holes exactly resemble thoseof the carbide particles shown in FIG. 6. If the time of treatmentdescribed in the invention had been extended on the sample shown in FIG.6 this pattern, as shown in FIG. 7, would have been obliterated sincemore of the matrix would have been etched away, more carbide particlesexposed and dissolved by the treatment.

DESCRIPTION OF THE PREFERRED EMBODIMENT The development of metal cuttingtools has been under intensive study during the last 50 years. This isdue to the economic pressure for greater machine output.

Primary development along this line has been made in the composition ofhigh speed cutting steels for cutting various metals or compositions ofmetals. These steels generally include in their analyses iron and carbonand certain metallic alloying constituents which add greatly to the lifeof the resultant tool.

These improved alloy cutting steels employ various proportions ofmolybdenum, chromium, vanadium, tungsten and cobalt, usually with eithermolybdenum or tungsten as the predominent alloy constituent. These alloyconstituents are frequently referred to as carbide formers."

Those skilled in the art of cutting tools designate under the term highspeed steel steel analyses containing various alloying metals in variousproportions to provide particular qualities and capabilities.

A metal cutting operation involves the movement of a tool, having acutting edge, relative to a workpiece to sever a chip from theworkpiece, which chip has movement along the rake face of the tool,there being a clearance between the bottom of the tool and the face ofthe workpiece by what is known as the relief angle. This mechanism iscommon to all metal cutting tools whose function is chip removal fromthe workpiece.

The specific embodiment herein illustrated and described in detail is ahigh speed metal cutting twist drill of the form illustrated in FIG. 1having a cutting and chip-engaging surface of the character illustratedin FIG. 7. This drill, as an example, is made of high speed steel of themolybdenum type, designated in the art by the symbol M-7, and comprisingcarbon and the alloying elements of molybdenum 8% percent, chromium 4percent, vanadium 2 percent and tungsten 1% percent. The invention isnot confined to a specific formula for the composition of the steel.Another typical composition frequently employed in the manufacture ofdrills is a steel having a composition designated in the art by thesymbol M-2. The invention is not to be confined to twist drills but isapplicable to high speed steel cutting tools generally which encounterthe same problems, but perhaps in somewhat less degree than the twistdrill.

As shown in FIG. 1 the twist drill 1 has a straight shank 2 at themounting end, and helical flutes 3, in this case two in number. Theseflutes have been ground into the body of the cylindrical blank fromwhich the drill is made, after hardening. Between the flutes are thehelical lands 4 upon the leading edges of which there are so-calledmargins 5 which at the cutting edges 66 extend to the full diameter ofthe drill and determine its effective diameter of cut. At the point endof the web, which is the thinnest part of the drill, there is thesocalled chisel edge 8. In the operation of the drill the chisel edge 8is forced into the metal to bring the cutting edges of lips 6-6 intoplay and the said cutting edges or lips sever the chips, one in eachflute. Said flutes in normal operation of the drill conduct the chipseither as continuous wirelike pieces, as shown in FIG. 3 at 9, oras'fragments which travel up through the flutes to the'outside' of thehole which the drill has formed.

At the bottom of the hole which the drill is forming, the cutting edgesor lips 6 sever material from the workpiece, and the chip from eachcutting edge is forced to move upwardly through the flutes 33 to theoutside of the hole. The material from the workpiece which goes to formthe chip must make a sharp rising movement against the face of the fluteimmediately adjacent to the lip, and it is at this point that the majorpart of the work of the drill is done. Metal from the workpiece issevered and raised to form the chip and where the friction of the chipon the edge and on the face of the flute is excessive the temperaturewill rise, sometimes to approximately the melting point of the materialof the workpiece, particularly in the case of soft, gummy metals such asaluminum and copper. The material from the workpiece tends to form abuildup or depositll on the cutting edge of the lip 6 and becomes weldedto it. As this deposit 11 builds up,the efficiency of the drill islowered and the friction of the drill in the hole becomes so great as toresult either in the drill no longer cutting and becoming ineffective orin actual breakage of the drill.

The prior art is aware that the resistance to chip formation and chipremoval from a cutting tool such as a drill may be facilitated bysurface treatment of the cutting tool. Such known treatments includesurface oxidation of the drill in a steam atmosphere to give a blackoxide coating to the treated surfaces. Another expedient is chromiumplating of the working surfaces of the drill. Both of thesemethodsimprove the life of the drill in some degree.

Practically the only surface treatment of the prior art which improvesdrill performance sufficiently to pay its cost is the steam oxidetreatment which gives the drill a coating of black oxide.

We have discovered that the serviceability and life of high speed twistdrills and similar cutting tools may be greatly improved by anelectrolytic surface treatment of the high speed steel which removes thesurface layer of tiny carbide particles as they originally appear on theworking surface so treated.

Drills made of high speed steel are, according to the present invention,subjected to the electrolytic treatment diagrammatically illustrated inFIG. 5. The electrolytic cell 12 is supplied with direct current overthe conductors 13 through the air operated switch 14 capable ofinterrupting heavy currents of the order of 500 amperes for a commercialinstallation. The switch 14 is controlled by a timer 15 which is set topredetermined time for the electrolytic treatment of the drill 16 as ananode in the electrolytic bath 17 consisting of sodium cyanide andsodium hydroxide in substantially equal proportions by weight dissolvedin water to make up an electrolyte at a Baume gravity of from l6l 7 in anewly prepared solution. The cathode 18 is a bar of mild steel.

Power may be supplied over leads 19 connected to a commercial source ofalternating current which supplies the rectifier 20 with power todeliver direct current at a voltage of 9 volts and up to 500 amperes fortreatment ofa multiplicity of drills at the same time. Instead of thesingle drill shown as subjected to the treatment, we may treat a batchof drills by using a tumbling barrel with insulated conductorsterminating in steel anodes exposed on the inside of the barrel tocontact the drills in the electrolytic bath. The anodes keep contactwith the drills as they are tumbled to maintain the electrolytictreatment while the drills change position for more nearly uniformeffect of the electrolytic action upon them. Ordinarily the tumblingbarrel is satisfactory to treat drills in diameters from one-eighththrough one-half inch in lots of the same size providing the number ofpieces in the lot is of sufficient quantity.

For treatment of drills smaller than one-eighth inch in diameter achannel type magnetic rack is used to hold the drills in position, thedirect current passing through the magnetic holding device.

Drills larger than one-half inch are held during treatment in amechanical type rack and the electrical connection made by means oflarge alligator clips. At times it is necessary to treat smallerquantities of drills in sizes from one-eighth inch through one-half inchthan would be suitable for handling in the tumbling barrel and thesesmaller quantities are treated in the same type racks and in the samemanner as described for the larger drills.

The electrolytic treatment of the invention leaves the surface of thedrill with a light gray color which makes the drill so treated readilydistinguishable from the drill with bright finish produced by theconventional grinding operations ordinarily used to grind drills tofinal dimensions.

We have run comparative tests, on the same workpiece and under the sameoperating conditions, of twist drills made of high speed steel andsurface treated according to the present invention and twist drills ofthe same high speed steel, surface treated in accordance with thepractice of the prior art, to compare effieacy of the prior art surfacetreatments with that of the present invention. Such tests have shownthat the surface treatment of the present invention produced cuttingtools-more specifically, twist drills-substantially superior inperformance to similar twist drills treated in accordance with theteaching of the prior art. This superiority is great enough to make thetreatment economically feasible.

We submit below a test report comparing drills prepared in accordancewith the present invention with those prepared in accordance with theprior art in connection with the drilling of holes in mild steel. Thematerial through which the drills operated was a plate of mild steel oneinch thick which called for the drilling of a deep hole, since a deephole is generally regarded as one which is four or more drill diametersdeep.

Drills Tested 3 dril ls No. 7 (0.2 010 inch dia,) General purposeJobbers Drills Vermont Style D-300 bright finish, no surface treatment.

3 drills same as above except steam oxidized. 3 drills same as firstgroup except surface treated according to the present process.

Test Material 1 inch thick mild steel: 149-156 Brinnel Hardness NumberSpeed 2850 R.P.M.; surface feet per minute Feed 0.0047 inch/rev., 13.4inch penetration per minute Coolant Soluble Oil Emulsion Purpose of testTo compare the preformance of drills of the present invention with theperformance of surface treated drills of the prior art, the test beingrun on a material (mild steel) widely encountered in drill opera- Drillsof the present invention While the above test shows that drills, surfacetreated by steam oxide treatment, will out-perform bright finisheddrills having no surface treatment, by 30 percent, drills treated inaccordance with the present invention give almost twice the increase inperformance of drills having steam oxide surface treatment on mildsteel.

In connection with the drilling of soft, gummy metals such asaluminum,copper, titanium and some of the stainless steels as well asother metals and their alloys, the superiority of drills of the presentinvention over drills treated in accordance with the prior art is muchgreater. 1n the drilling of aluminum and the like the material from theworkpiece welds onto the cutting edge of the drill and builds up in theflutes destroying the efficiency of the drill as a cutting tool, Thechip, instead of showing a clean cut surface, resembles more nearly adrawn wire which continues on from the cutting edge through thecorresponding flute and out of the hole.

The variable of current density, temperature, concentration of solution,and time are not found to be too critical but nevertheless should becontrolled between certain limits.

Current Density The current density generally runs approximately 0.5 to2.0 amperes per square inch of the parts being treated. A lesser currentdensity and a longer time would accomplish similar results. In practicethe total direct current amperes into the bath generally remain constantand the time in the bath is used for control. Temperature The bath ismaintained between and 145F. By an electrical heater in the bath andthermostatic control, normally the bath is kept between and F.Concentration of Solution The new solution is made up with 12-15 ouncesof sodium hydroxide and 16-20 ounces of sodium cyanide per gallon ofwater. Baume runs l617 for the new solution but as weeks of use pass bygradually rises to around 31 and then tends to level off. Theconcentration of both chemicals in the bath is periodically maintainedby the addition of chemicals as required based upon conventionalchemical analysis.

Time

The time varies between 3 to 10 minutes depending on the total weightand the surface area versus unit weight relationship of the particulartype tools being treated. For example, with a total of 200 directcurrent amperes going through the bath and load, a light load of V8 inchdrills in the tumbling barrel might require 3 minutes and a large loadof the same drills 10 minutes to complete the treatment.

Surface color provides a fair indication for the extent of thetreatment. A light gray color is desired. Darker gray indicatesovertreatment which generally means that etching has progressed beyondjust the surface layer and that carbide particles further down into thetool have also been removed, all of which is undesirable.

Test runs comparing the drill of the present invention with the drillsprepared by surface treatment in accordance with the prior art showimprovement in the drills of this invention in number of holes drilled,generally in the range of from 2 to 4 times as many holes drilled bydrills of the present invention as by drills prepared in accordance withthe prior art. The improvement shown in the specific test above reportedis in about the lowermost range of improvements shown by tests onvarious metals which we have conducted.

We claim:

1. Electrolytic surface treatment of a cutting tool of high speed steelwhich contains iron and carbon and one or more carbide-forming alloyingmetals and hard carbide particles in the body and on the surface of thesteel, which comprises subjecting the tool as an anode to electrolysisof a unidirectional current in an aqueous bath of substantially equalparts of sodium cyanide and sodium hydroxide at an initial Baume of l6l7 and at a temperature of from l35-145F for a period of fromapproximately 3 to 10 minutes at a current density of from approximately0.5 to 2 amperes per square inch to remove said carbide particles fromthe surface which is treated.

2. A method of surface treating a steel cutting tool having chipengaging surfaces to reduce the friction of said chip-engaging surfaceswith the chip, which method comprises subjecting said surfaces toelectrolytic treatment with the tool as an anode in the electrolyticbath of substantially equal parts of sodium hydroxide and sodium cyanidein water at a Baume of approximately 16 at the start and at atemperature of approximately 135 to 140F at a current density ofapproximately 0.5 to 2 amperes per square inch for a period of from 3 tominutes to remove carbide particles from chip engaging surfaces of thetool.

3. The method of claim 2 wherein the tool is a twist drill having lands,flutes and a point, said point having cutting edges.

4. The method of smoothing tool marks and removing exposed carbideparticles from the working surface of a high speed steel cutting toolcontaining hard carsulting carbide particles distributed throughout ther same, said drill comprising a shank, a body having flutes, lands,margins, a web, lips and cutting edges, and electrolytically removingexposed carbide particles from the surface of the flutes and cuttingedges whereby the resulting twist drill will give superior performanceon drilling soft, tough metals by virtue of the reduced friction betweenthe surfaces of the drill and the workpiece and the chips producedtherefrom.

2. A method of surface treating a steel cutting tool having chipengaging surfaces to reduce the friction of said chip-engaging surfaceswith the chip, which method comprises subjecting said surfaces toelectrolytic treatment with the tool as an anode in the electrolyticbath of substantially equal parts of sodium hydroxide and sodium cyanidein water at a Baume of approximately 16* at the start and at atemperature of approximately 135* to 140*F at a current density ofapproximately 0.5 to 2 amperes per square inch for a period of from 3 to10 minutes to remove carbide particles from chip engaging surfaces ofthe tool.
 3. The method of claim 2 wherein the tool is a twist drillhaving lands, flutes and a point, said point having cutting edges. 4.The method of smoothing tool marks and removing exposed carbideparticles from the working surface of a high speed steel cutting toolcontaining hard carbide particles exposed at the working surface whichcomprises subjecting the said working surfaces to electrolysis with thecutting tool serving as an anode in an electrolyte of substantiallyequal parts of sodium hydroxide and sodium cyanide.
 5. Method ofproducing a high speed steel twist drill of superior performance indrilling relatively soft, tenacious metals which comprises forming adrill of high speed steel which contains iron and carbon and one or morecarbide forming alloying metals and contains resulting carbide particlesdistributed throughout the same, said drill comprising a shank, a bodyhaving flutes, lands, margins, a web, lips and cutting edges, andelectrolytically removing exposed carbide particles from the surface ofthe flutes and cutting edges whereby the resulting twist drill will givesuperior performance on drilling soft, tough metals by virtue of thereduced friction between the surfaces of the drill and the workpiece andthe chips produced therefrom.